The social networking giant, led by the hoodie-wearing Mark Zuckerberg, is going to sell more than $16-billion of shares to frenzied investors scrambling not to miss out on the biggest IPO of the year..history?

Update: Due to strong demand, Facebook will sell 25% more shares than it originally planned.

The IPO will give Facebook a staggering $96-billion$104-billion valuation and, if it's possible, subject the company to even more scrutiny, fascination and criticism.

And while I'm sure Facebook shares will soar above the $34 to $38 offering price when it starts trading tomorrow, I personally wouldn't buy them, other than to flip them to some sucker looking to scramble on to the Facebook bandwagon.

It's not because I've been ambivalent for Facebook for a long time, it's that Facebook is hitting the IPO market at its zenith, and it has nowhere to go but down.

In the short-term, Facebook won't become any less popular or see the number of users - currently more than 900 million - decline, but there are growing indications the Roman Empire of the social media landscape may be crumbling.

How come? Here are some reasons:

1. Social media fatigue: As much as social media has become an integral part of our lives, it is also getting overwhelming. All the updates, tweets, check-ins, pinning and connecting is consuming more time and energy. A digitally-connected friend of mine told me he hadn't used Pinterest yet because he had too much social media on his plate already, while his use of Path has evaporated.

2. Facebook is no longer hot and sexy. According to a recent poll, nearly 50% of people in the U.S. think Facebook is a "fad". It's certainly an enormous fad but you do wonder whether the need to be on Facebook is starting to disappear.

3. A growing number of advertisers are questioning whether Facebook is a good advertising medium. GM, for example, plans to pull $10-million of advertising from Facebook, while maintaining its 30+ Facebook Pages to maintain a strong presence. The bottom line for GM and, arguably, other advertisers is Facebook users don't look or click on many ads.

4. Mobile, which accounts for nearly half of Facebook's daily users, is popular but Facebook hasn't figure out how to make money from it. Unlike the Web in which Facebook slapped up contextual and highly-targeted advertising, mobile is a different beast when it comes to monetization. While more and more people have smartphones, mobile advertising is still in its early stages.

5. Facebook's need to drive financial results is going to put the emphasis on making more money, which means the overall experience could become more commercial, which runs counter to how many people like to use Facebook as a communications medium. A sign of things to come may be Facebook's current effort to test the idea of a "promoted status update" feature that would see users pay to have their updates highlighted.

While I'm bearish on Facebook, I expect tomorrow to be a triumphant day for Facebook, Zuckerberg and the company's investors, including Goldman Sachs, Yuri Milner and Zuckerberg, who are selling some of their shares as part of the offering.

In the long-run, however, I would not be surprised to see the shares sag - much like other much-hyped IPOs such as GroupOn.